| 摘要 |
PURPOSE:To surely detect a drop-out with simple circuit constitution by monitoring that the signal level of a digitized read signal is increased or reduced continuously during a prescribed number of samplings. CONSTITUTION:A most significant bit continuity number detecting circuit 34 consists of counter or the like, and a detection output is generated when the most significant bit has the same logic continuously during a prescribed number of samplings. This detection output is supplied as a drop-out detection signal to a drop-out correcting circuit. Data of the most significant bit of a subtraction signal is extracted by a most significant bit extracting circuit 42, and it is monitored by the most significant bit continuity number detecting circuit 43 that the most significant bit has the same logic continuously during a prescribed number of samplings, that is, the signal level is continuously increased (or reduced)) for a time longer than that for the absence of drop-out thereby detecting the drop-out.
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